I've found the best way to build discipline is to find someone with discipline and have them keep you accountable. This could be a mentor of some kind. Granted finding that may be equally as hard as doing it on your own.

Also you don't necessarily need discipline in the actual thing you want to do - you just need to know what it means to be disciplined in something and then you can extrapolate your behavior in discipline itself to then be disciplined in something.